A broad class of medical subspecialties, including cardiology, endocrinology, hematology, neurology, gastroenterology, urology, ophthalmology, and otolaryngology, to name a few, rely on accurate and timely patient information for use in aiding health care providers in diagnosing and treating diseases and disorders. Often, proper medical diagnosis requires information on physiological events of short duration and sudden onset, yet these types of events are often occur infrequently and with little or no warning. Fortunately, such patient information can be obtained via external, implantable, cutaneous, subcutaneous, and manual medical devices, and combinations thereof. For example, in the area of cardiology, implantable pulse generators (IPGs) are medical devices commonly used to treat irregular heartbeats, known as arrhythmias. There are three basic types of IPGs. Cardiac pacemakers are used to manage bradycardia, an abnormally slow or irregular heartbeat. Bradycardia can cause symptoms such as fatigue, dizziness, and fainting. Implantable cardioverter defibrillators (ICDs) are used to treat tachycardia, heart rhythms that are abnormally fast and life threatening. Tachycardia can result in sudden cardiac death (SCD). Finally, implantable cardiovascular monitors and therapeutic devices are used to monitor and treat structural problems of the heart, such as congestive heart failure, as well as rhythm problems.
Pacemakers and ICDs, as well as other types of implantable and external medical devices, are equipped with an on-board, volatile memory in which telemetered signals can be stored for later retrieval and analysis. In addition, a growing class of cardiac medical devices, including implantable heart failure monitors, implantable event monitors, cardiovascular monitors, and therapy devices, are being used to provide similar stored device information. These devices are able to store more than thirty minutes of per heartbeat data. Typically, the telemetered signals can provide patient device information recorded on a per heartbeat, binned average basis, or derived basis from, for example, atrial electrical activity, ventricular electrical activity, minute ventilation, patient activity score, cardiac output score, mixed venous oxygen score, cardiovascular pressure measures, time of day, and any interventions and the relative success of such interventions. In addition, many such devices can have multiple sensors, or several devices can work together, for monitoring different sites within a patient's body.
These telemetered signals can be remotely collected and analyzed using an automated patient care system. One such system is described in a related, commonly-owned U.S. patent application, Ser. No. 09/324,894, filed Jun. 3, 1999, pending. The telemetered signals are recorded by an implantable medical device, such as an IPG or monitor, and periodically retrieved using an interrogator, programmer, telemetered signals transceiver, or similar device, for subsequent download. The downloaded telemetered signals are received by a network server on a regular, e.g., daily, basis as sets of collected measures which are stored along with other patient records in a database. The information is analyzed in an automated fashion and feedback, which includes a patient status indicator, is provided to the patient.
While such a system can serve as a valuable tool in automated, remote patient care, the accuracy of the patient care, particularly during the first few weeks of care, and the quality of the feedback provided to the patient would benefit from being normalized to a reference baseline of patient wellness. In particular, a starting point needs to be established for each individual patient for use in any such system in which medical device information, such as telemetered signals from implantable and external medical devices, is continuously monitored, collected, and analyzed. The starting point could serve as a reference baseline indicating overall patient status and wellness from the outset of remote patient care.
In addition, automated remote patient care poses a further challenge vis-a-vis evaluating quality of life issues. Unlike in a traditional clinical setting, physicians participating in providing remote patient care are not able to interact with their patients in person. Consequently, quality of life measures, such as how the patient subjectively looks and feels, whether the patient has shortness of breath, can work, can sleep, is depressed, is sexually active, can perform activities of daily life, and so on, cannot be implicitly gathered and evaluated.
Reference baseline health assessments are widely used in conventional patient health care monitoring services. Typically, a patient's vital signs, consisting of heart rate, blood pressure, weight, and blood sugar level, are measured both at the outset of care and periodically throughout the period of service. However, these measures are limited in their usefulness and do not provide the scope of detailed medical information made available through implantable and external medical devices. Moreover, such measures are generally obtained through manual means and do not ordinarily directly tie into quality of life assessments. Further, a significant amount of time generally passes between the collection of sets of these measures.
In addition, the uses of multiple sensors situated within a patient's body at multiple sites are disclosed in U.S. Pat. No. 5,040,536 ('536) and U.S. Pat. No. 5,987,352 ('352). In the '536 patent, an intravascular pressure posture detector includes at least two pressure sensors implanted in different places in the cardiovascular system, such that differences in pressure with changes in posture are differentially measurable. However, the physiological measurements are used locally within the device, or in conjunction with any implantable device, to effect a therapeutic treatment. In the '352 patent, an event monitor can include additional sensors for monitoring and recording physiological signals during arrhythmia and syncopal events. The recorded signals can be used for diagnosis, research or therapeutic study, although no systematic approach to analyzing these signals, particularly with respect to peer and general population groups, is presented.
Thus, there is a need for an approach to determining a meaningful reference baseline of individual patient status for use in a system and method for providing automated, remote patient care through the continuous monitoring and analysis of patient information retrieved from an implantable medical device. Preferably, such an approach would establish the reference baseline through initially received measures or after a reasonable period of observation. The reference baseline could be tied to the completion of a set of prescribed physical stressors. Periodic reassessments should be obtainable as necessary. Moreover, the reference baseline should preferably be capable of correlation to quality of life assessments.
There is a further need for an approach to monitoring patient wellness based on a reference baseline for use in an automated patient care system. Preferably, such an approach would dynamically determine whether the patient is trending into an area of potential medical concern, including indicating disease onset, progression, regression, and status quo.
There is a further need for an approach to determining a situation in which remote patient care is inappropriate based on a reference baseline of patient wellness. Preferably, such an approach would include a range of acceptance parameters as part of the reference baseline, thereby enabling those potential patients whose reference baseline falls outside those acceptance parameters to be identified.